
\begin{tikzpicture}[scale=3, ang/.style={mark angle={green}{5mm}{1.2}}]
  \coordinate[label=below:$C$] (C) at (0,0);
  \coordinate[label=above:$D$] (D) at (140:{sin(80)});
  \coordinate[label=below:$B$] (B) at ({-sin(60)},0);
  \coordinate[label=below:$A$] (A) at ({-sin(60)-sin(80)},0);
  \pic[ang, "$60^\circ$"] {angle=B--D--C};
  \pic[ang, "$40^\circ$"] {angle=D--C--B};
  \pic[ang, "$?$"] {angle=B--A--D};
  \draw (A) -- (C) -- (D) -- cycle (B) -- (D);
  \draw[blue] (A) -- (B) (C) -- (D);
\end{tikzpicture}
